/*
 *    This program is free software; you can redistribute it and/or modify
 *    it under the terms of the GNU General Public License as published by
 *    the Free Software Foundation; either version 2 of the License, or (at
 *    your option) any later version.
 *
 *    This program is distributed in the hope that it will be useful, but
 *    WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *    General Public License for more details.
 *
 *    You should have received a copy of the GNU General Public License
 *    along with this program; if not, write to the Free Software
 *    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  */

/*
 *    ExponentialFormat.java
 *    Copyright (C) 2002 University of Waikato, Hamilton, New Zealand
 *
 */

package weka.core.matrix;

import weka.core.RevisionHandler;
import weka.core.RevisionUtils;

import java.text.DecimalFormat;
import java.text.FieldPosition;

/**
 * @author Yong Wang
 * @version $Revision: 1.4 $
 */
public class ExponentialFormat extends DecimalFormat implements RevisionHandler {

	/** for serialization */
	private static final long serialVersionUID = -5298981701073897741L;

	protected DecimalFormat nf;
	protected boolean sign;
	protected int digits;
	protected int exp;
	protected boolean trailing = true;

	public ExponentialFormat() {
		this(5);
	}

	public ExponentialFormat(int digits) {
		this(digits, false);
	}

	public ExponentialFormat(int digits, boolean trailing) {
		this(digits, 2, true, trailing);
	}

	public ExponentialFormat(int digits, int exp, boolean sign, boolean trailing) {
		this.digits = digits;
		this.exp = exp;
		this.sign = sign;
		this.trailing = trailing;
		nf = new DecimalFormat(pattern());
		nf.setPositivePrefix("+");
		nf.setNegativePrefix("-");
	}

	public int width() {
		if (!trailing)
			throw new RuntimeException("flexible width");
		if (sign)
			return 1 + digits + 2 + exp;
		else
			return digits + 2 + exp;
	}

	public StringBuffer format(double number, StringBuffer toAppendTo,
			FieldPosition pos) {
		StringBuffer s = new StringBuffer(nf.format(number));
		if (sign) {
			if (s.charAt(0) == '+')
				s.setCharAt(0, ' ');
		} else {
			if (s.charAt(0) == '-')
				s.setCharAt(0, '*');
			else
				s.deleteCharAt(0);
		}

		return toAppendTo.append(s);
	}

	private String pattern() {
		StringBuffer s = new StringBuffer(); // "-##0.00E-00" // fw.d
		s.append("0.");
		for (int i = 0; i < digits - 1; i++)
			if (trailing)
				s.append('0');
			else
				s.append('#');

		s.append('E');
		for (int i = 0; i < exp; i++)
			s.append('0');

		return s.toString();
	}

	/**
	 * Returns the revision string.
	 * 
	 * @return the revision
	 */
	public String getRevision() {
		return RevisionUtils.extract("$Revision: 1.4 $");
	}
}
